Hi there, you have to log out of the account you created and log into the admin account, then the apps can be deleted from your Mac. By the way, you can only delete specific pre-installed apps coming with macOS (like Keynote, Pages, Numbers, GarageBand, and iMovie) and third-party apps from your computer, the rest of the built-in apps cannot be deleted since Apple regards them as parts of the operating system.
Furthermore, these apps have accumulated many user files or caches. If you want to delete them completely, you must also clean the associated files. You can utilize a professional app remover -- iBoysoft MagicMenu here. It gathers all associated files of the app being deleted, and you can choose what to delete along with the app uninstall. It's quite convenient to use!